Re: [Phys-l] energy is well defined.

[Leon de Oliveira <leondeolive@gmail.com>]

Well Ken,

I have given a fairly concise definition to my class and I would like to 
see if it stands up to the listserv.

Energy - a conserved substance like quantity that can be transferred 
from one body to another or transformed from one form to another.

That is the basic definition I use to get the students thinking about it 
as a conserved quantity. It also allows for the transfer of the energy 
from body to body and from form to form. We also talk about the forms 
objects store energy in. A moving object stores Kinetic energy. This is 
to show that energy is constantly being shifted around from one form or 
body to another. Let me know what you think.

Leon

Ken Fox wrote:
> I don't know if anyone else has read John's notes on Energy. They are very
> interesting to me and quickly are over my head. ( 2 hot potatoes can do more
> work as long as we keep the cold one as well, I think.)
>
> I want to teach energy to my high school students and would love a
> definition and was excited to be told that it is well defined. Then I read
> the part of the notes named "Definition of Energy" and several sentences
> jumped out at me:
> 1."It is more important to *understand* energy than to *define* energy. We
> can and will define it, but the definition is not super-simple nor
> super-concise. The concept of energy is so fundamental that there is no
> point in looking for a concise definition in terms of anything more
> fundamental."
> 2."Energy is somewhat abstract. There is no getting around that. You just
> have to get used to it – by accumulating experience, seeing how energy
> behaves in various situations. As abstractions go, energy is one of the
> easiest to understand, because it is so precise and well-behaved."
> 3."The most important thing about energy is its role in the law of
> conservation of energy,...."
>
> I am still looking for the well defined statement of energy, suitable for my
> neophytes, but I feel better that what have done in my classes for 40 years
> falls into these 3 statements.
>
> Ken Fox
>
>
>
> On Feb 16, 2008 8:53 AM, John Denker <jsd@av8n.com> wrote:
>
>   
> > In the context of
> >  http://www.av8n.com/physics/energy-counterexample.htm
> >
> > On 02/16/2008 06:51 AM, carmelo@pacific.net.sg wrote:
> >
> >     
> > > How about heat or thermal energy generated when sands are continuously
> > > falling at constant rate on a moving conveyor belt?
> > >       
> > Well, how about it?
> >
> >     
> > > Electromagnetic
> > > energy generated by friction to what extent measurable?
> > >       
> > What about it?
> >
> >     
> > > Zero-point energy measurable?
> > >       
> > Yes, it is measurable.  What's the point?
> >
> >     
> > > Energy is *well* defined as "capacity to perform work" or "ability to
> > > perform work"?
> > >       
> > No, that's not a good definition, for reasons explained in detail at
> >  http://www.av8n.com/physics/thermo-laws.htm#sec-workability
> >
> > Note that the existence of a bad definition does not disprove
> > the existence of a good definition.
> >
> >     
> > > It is, of course, better for the students to learn from something
> > > concrete, then to abstract...
> > >       
> > Maybe that's why Feynman started with an exceedingly concrete
> > example of conservation (Dennis and the blocks) before
> > abstracting away the concreteness.
> >
> > Maybe that's why
> >  http://www.av8n.com/physics/thermo-laws.htm#sec-energy
> > also starts with a series of more-or-less concrete examples
> > before abstracting away the concreteness.
> >
> > ========================
> >
> > Bottom line:  This brings us to a grand total of zero valid
> > counterexamples.
> >
> > _______________________________________________
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> >
> >     
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